The maximum amplitude a digital system can represent. Also known as "full code", a signal has reached full scale when it has reached the maximum (or minimum) representable value. Theoretically this occurs when all bits are 1s, but this is a simplified analysis. Full scale also occurs when the minimum value (or maximum rarefaction amplitude is reached, which would be represented as all 0s. Further, many digital systems use other digital encoding methods, such as two's complement wherein all 1s or all 0s actually occur around the zero crossing, and the maximum and minimum values are not as simply described.
Once a signal has reached full scale all headroom has been utilized, and any further increase in gain results in an error known as clipping.
An important observation is that digital information only represents its analog equivalent, and must be reconstructed in order to reveal the original information. It is possible, therefore, for the signal represented by the digital data to exceed full scale even if the digital data does not.
References and External Links
Nika Aldrich explores the consequences of exceeding full scale in digital audio systems in: